While this makes it easier to use- you should always use a keypair to login via SSH anyway. However you should also always use a password along with it. The password might not need to be as complex imho as without the key pair, but it is still important. Otherwise anyone with access to your box has instant access to your server as well.
Yes. The author of the article does not appear to be aware you can add your keys to ssh-agent (with ssh-add) and that way just type your password once.